1. Field of the Invention
The present invention relates to a radial seal of a rotary piston engine with a trochoidal-shaped mantel raceway or casing inner peripheral surfacing and a multi-corner piston means. Sealing strips are arranged in radial grooves in the corners of the piston means; the sealing strips under pressure of the working or operating chambers of the rotary piston engine engage against the mantel raceway or casing inner peripheral surfacing and respectively also engage against an under-pressure-side groove wall. The sealing strips have perforations or breakthroughs in the sealing surfaces thereof coming into engagement along the groove walls.
2. Description of the Prior Art
Such sealing strips are exposed and subjected to a tipping, tilting or pitching moment under the working or operating pressure effective upon a part or portion of the sealing strips projecting beyond the groove edges and under the effect or result of rolling friction, rubbing or abrasion of the crest, arch, dome or apex thereof along the mantel raceway or casing inner peripheral surfacing along which the sealing strips move; such tipping, tilting or pitching moment can lead to jamming of the sealing strip in the groove and with that can lead to hindrance or restraint of movement, to hammering, to leakiness and to undue wear on the sealing strip and mantel raceway or casing inner peripheral surfacing.
Consequently an endeavor or effect is made to keep and maintain the groove clearance of the sealing strip as small as possible in order to prevent any tipping, tilting or pitching of the seal strip. With a groove clearance that is too small or nominal however, the groove gap resulting on the pressure side along the low-pressure-side groove wall during engagement of the sealing strip is too narrow in order to permit and allow the working or operating pressure in the groove base or bottom to reach or come below the sealing strip in a timely manner. The sealing strip then cannot seal-off with full pressure of engagement with respect to the mantel raceway or casing inner peripheral surfacing.
In order to eliminate or remove this disadvantage, there was proposed in German Pat. No. 12 23 614 Paschke dated Mar. 9, 1967 (corresponding to U.S. Pat. No. 3,185,387--Paschke dated May 25, 1965) to reduce the cross section of the radially inner part of the sealing strip in peripheral direction with respect to the upper part coming into engagement against the groove walls in the region of the groove edges and additionally in the lower part to provide continuous perforations or breakthrough means in peripheral direction, whereby the space for the flowing-in of the pressure gas is adequately enlarged. The arrangement of such large spaces or chambers however results in the disadvantage that the filling-up thereof with pressure gas requires a time delay, which does not permit and allow an intermediate seal effectiveness, which most of all is important at higher rotary speeds. The aforementioned German Patent consequently already proposes to close the recess spaces or chambers between the sealing strip and the groove with filler pieces (fairing) or corresponding configurations and construction of the groove base or bottom. This in itself is a contradiction to the teaching of this patent disclosure and this proposal is not adequately explained either in the description or in the drawings. The proposed recesses, notches, cutouts or openings additionally have the disadvantage that the under-pressure-side sealing surface is too small between the sealing strip and the groove wall.
In the U.S. Pat. No. 4,403,930--Kodama dated Sept. 13, 1983 for a Multi-Piece Apex Seal Structure for a Rotary Piston Engine there is proposed a sealing strip which is divided in a plane located in peripheral or circumferential direction, with which the radially inner part is narrower with respect to the radially outer part adjoining or engaging against the mantel raceway or casing inner peripheral surfacing and is shiftable in circumferential or peripheral direction.
The lower part of the seal length strip is shifted toward the under-pressure-side groove wall via the operating pressure, whereby an expanded or widened access or entry pass into the groove base is obtained for the pressure gas, without receiving too wide and only belated fillable spaces or chambers. Additionally, there results a greater elasticity and close contact or adhesion of the sealing strip with respect to temperature-conditioned or temperature-limited unevenness and distortion of the mantel raceway or casing inner peripheral surfacing.
The advantage of the narrowing or constriction of the groove made possible therewith however is again nullified by the considerable shortening of the sealing strip in radial direction, since only the radially outer part of the sealing strip can be considered, because the possible canting or tipping angle is enlarged with radial shortening of the sealing strip with a given groove width.
An object of the present invention accordingly is to provide a sealing strip, with which an adequate or sufficiently quick access or entry of the pressure gas underneath the sealing strip is made possible; this occurs with the smallest possible dead-space formation being encountered therewith; furthermore a wide-surface engagement of the under-pressure-side thereof against the groove wall is attained therewith also provided are higher elasticity and close contact and snug adherence as to the unevenness and distortions of the mantel runway or casing inner peripheral surfacing. This object is met and fulfilled with the features of the present invention.